Theoretical and experimental studies on the vibrational spectra of 3-quinolinecarboxaldehyde

Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra including far region) of 3-quinolinecarboxaldehyde. Hartree–Fock (HF) and density functional theory (DFT) B3LYP calculations have been employed with the 6-311++G(d,p) basis set for investigating the structural and spectroscopic properties of the Rot 1 and Rot 2 conformers of 3-quinolinecarboxaldehyde. The B3LYP frequencies are closer to the experimental frequencies than the HF frequencies, but scaled frequencies of both HF and B3LYP agree almost perfectly with the experimental frequencies. The Rot 1 conformer has been found more stable than the Rot 2 conformer. The scaled vibrational frequencies of Rot 1 conformer also agree slightly better than those of the Rot 2 conformer compared with the experimental frequencies. These indicate that 3-quinolinecarboxaldehyde has Rot 1 conformation in its ground state.

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► Frequencies and geometries of Rot 1 and Rot 2 conformers of 3-quinolinecarboxaldehyde were calculated.
► The calculated HF and B3LYP results were compared with FT-IR, FT-FIR, and Raman data.
► The conformational analysis of 3-quinolinecarboxaldehyde were performed.